18 F-FDG PET/CT of Sacrococcygeal Pilonidal Sinus Carcinoma.

Pilonidal sinus carcinoma is rare, with a poor prognosis, often misinterpreted as infection or perianal fistula. We present 18 F-FDG PET/CT imaging in a 69-year-old woman with a chronic pilonidal sinus that progressed to an abscess and drained spontaneously. The retrorectal-precoccyx irregular mass with sinus tract formation and apparent glucose metabolism, connecting with an intergluteal cyst, was confirmed pathologically as pilonidal sinus carcinoma.